Hi Maya,
Write a customer exit in BW for the prompt so that whenever it runs in BW it should take yesterday's date.
Then purge data in your webi report and save the report.
While scheduling do not mention values in Prompt.
Code in BW will be like:
WHEN 'ZC_DATE1' .
CLEAR C_DATE .
C_DATE = SY-DATUM - 1 .
L_T_RANGE-SIGN = 'I'.
L_T_RANGE-OPT = 'EQ'.
L_T_RANGE-LOW = C_DATE .
APPEND L_T_RANGE TO E_T_RANGE.
Regards
Sheetal Sharma